Screen-plate for straining paper-pulp.



Patented Oct. 30,- |900. E. J. WELCH. SCREEN PLATE FOR STRAINING PAPER PULP.

(Application filed Mar. 20, 1900.) (lo hdsl.)

UNITED STATES PATENT FFIC.

EDWARD WELCH, OFFITCHBURG, MASSACHUSETTS.

SCREEN-PLATE FOR STRAl-NING PAPER-PULP.

sPEeIMF'IcATIoNfrming part of Letters Patent No. 660,764, dated october 3o, 190e. iteration sied March 20,1900. 3 serai No; 9,383. dit moda.)

To a/ZZ whom t may concern:

Be it known that I, EDWARD J. WELCH, a citizen of the United States, residing at Fitchburg, in the county of Worcester and State of Massachusetts, have invented a new and useful Screen-Plate for Strainin g Paper-Pnl p,

. of which the following is a specification.

end of this specification.

In the accompanying drawings, Figure l is a transverse sectional view of a screen-plate constructed according to this invention. Fig. 2 is a plan view of the same, partially broken away. Fig. 3 is a sectional View taken on the line 3 3 of Fig. 2; and Fig. l is aview similar to Fig. 2, illustrating a slightly-modified form of construction.

In the manufacture of paper, and especially in the manufacture of paper from Wood-pulp, it is necessary that the stock should be refined by being drawn or forced through comparatively fine screens. To produce the liner grades of papers, the orifices or slots of the screen-plates are extremely narrow, often being less than one-hundredth of an inch in width. Screen-plates which have heretofore been used for straining paper-stock have ordinarily been formed from solid brass plates. These brass plates first have comparatively wide or coarse grooves or cuts milled out of their rear faces. These coarse cuts extend through the plate nearly, but not quite, to the top face thereof, the remaining metal of the plate being sawed through or slotted with an extremely-fine cutter which will make slots of the narrow width required. An ordinary screen-plate as thus constructed can be used for straining paper-stocks for only a comparatively short time on account of the enlargement of its fine slots due to the wear or abrasion of the paper-stock as it is drawn through the screen, and especially on account of the presence of sulfurous 'and other acids in the stock. On this account the screen-plates employed for straining paper-stock frequently require to be replaced or repaired.

To repair an ordinary screen-plate of the constructiony before described, it has heretofore been proposed to roll down or compress the surface of the worn-out plate,'so as to tend to close the worn or enlarged slots in the face thereof and to recut the screen-plate after the same has thus been rolled down. By this method of rolling down and then recutting the Worn-out screen-plates the same screenplates may be used for two or three successive times; but when the screen-plates have been recut a number of times the entire surface of the plate between the coarse cuts and its upper face becomes worn out, rendering the plate entirely useless.

The especial object of mypresent invention is to provide a screen-plate which may be made to wear longer than the screen-plates of the construction above described and which m`ay be readily and eiiiciently repaired as frequently as may become necessary.

To this end a screen-plate constructed ac- 8o cording to my present invention comprises a main plate having a plurality of gridironed or coarsely-slotted sections therein. The u pper surface of the main plate over the gridironed sections is recessed, leaving side ribs 85 at the edge of the plate and one or more intermediate ribs between the gridironed sections of the plate. Secured in the recesses of the main plate, and' preferably having dovetailed edges engaging said recesses, are top 9o plates, which are preferably sweated or sol-v dered in. position, so that their surfaces are flush with the tops of the side and intermediate ribs of the main plate. As shown in the accompanying drawings, the main plate herein illustrated is provided with a plurality of gridironed or coarsely-slotted sections lO.

In the present instance I have illustrated a plate having three gridironed sections, although in practice I have employed screenroo plates having two such sections. Along two of its sides the main screen-plate is provided with screw-holes 11 for securing the screenplate to a ledge or rabbet inside of the ordinary screen-box. The upper surface of the main plate is recessed over each of its coarselygrooved or gridironed sections 10, leaving edge ribs 12 at the sides of the plate and intermediate ribs 13 between the sections lO.

Fitting into the recesses in the surface of the main plate, and preferably having dovetailed edges, are the top plates 14, which are rstsecured inplace by being sweated or soldered in position and lthen are grooved or slotted with a ne saw or cutter. The slots in the top plates of the screen preferably extend transversely in said top plates 14, as shown in Fig. 2, although in some instances the slots or grooves may extend longitudinally with respect to the top plates 14, as shown in Fig. 4. In both constructions the surfaces of the top plates 14 are preferably flush with the side ribs 12 and intermediate ribs-13 of the main plate.

If desired, the top plates 14 of a screenplate constructed according to my invention may be made of harder metal than the body portion of the screen-plate, and on this account I have provided a construction which is more durable than the ordinary form of screen-plate formed by cutting out or grooving a solid plate of brass.

In addition to this a screen-plate constructed according to my invention may be much more readily repaired than screen plates which have heretofore been used.

When it is desired to repair a screen-plate of my invention, it is first taken out of the screening-box or position where the same is used and is heated sufficiently to allow the top plates to be loosened and taken out. The top plates which are removed are replaced by new top plates, which are first soldered or sweated in position and are then cut or slotted, and inasmuch as the position of the screw-holes l1 remains unchanged a screenplate constructed according to my invention may be accurat-ely and quickly replaced in the position from which the same was taken. In addition to this the screen-plates may be repaired as frequently as may become necessary, a single main plate being capable of wearing out a considerable number of replaceable top plates.

In actual use screen-plates constructed according to my invention have the advantage of presentinga greater area of screening-surface than in the ordinary forms of plates heretofore employed. This is due to the fact that the cutter which is used for milling out the gridironed sections of the main plate will extend through the plate far enough so that the arcs formed at the sides of the rear ribs 12and intermediate ribs 13 will be comparatively short and more nearly upright than in the ordinary plates constructed according to my inventionv arises from the fact that the top plates when soldered or sweated into place in their sockets are held with perfect rigidity, so that the 1 main plate and top plates form practically one integral structure in which the parts are not liable to spring or warp apart when the plate is bent or defiected under the screening pressure.

I am aware that it is not new to provide a screenplate with a nely -slotted top plate which is held in place on a main or supporting plate by screws. The actual use of such plates is objectionable, however, for the reason that the plates are liable to warp orspring apart when subjected to screening pressure, so as to leave a crack or space between said plates,and myinvention is to be distinguished from the composite plates of this character not only for the reason that each of my plates forms practically one rigid integral structure, but also by reason of the fact that the top plates of my device may be removed and replaced without covering up or altering the location of the screw-holes which receive the screws for holding the screen-plates in place in a screening-box, which fact permits the screen-plates to be replaced with absolute accuracy after they have been repaired or renewed. y

I am aware that changes may be made in the details of construction and in the relative proportions of screen-plates constructed according to my invention, and I do not wish, therefore, to be limited to the form herein shown and described; but

What I do claim, and desire to secure by Letters Patent of the United States, is-

1. As an article of manufacture, a screenplate for straining paper-stock comprising a main plate having a gridironed section, and having a recess in its upper surface over said gridircned section, arranged to leave raised side ribs at the edges of the plate, and a top plate fitting into said recess and soldered or sweated in place so that its surface Will be ush with the top of the side ribs, substantially as described.

2. As. an article of manufacture, a screenplate for straining paper-stock, comprising a main plate 10 having coarsely-grooved gridironed sections, and having recesses above said gridironed sections, arranged to leave IOO IOS

IIO

IIS

raised side ribs i2 at lshe edges of the plate, In testimony whereof; have hereunto set and raised intermediate ribs 13, the side ribs my hand in the presence of two subscribing 12 being,r provided with perforations or screw- Witnesses.

holes, and a top plate fitting into each recess EDWARD J. WELCH. 5 in the main plate, and soldered or sweated in /Vitnesses:

place so that its surface is flush with the top PHILIP W. SOUTHGATE,

of the ribs, substantially as described. LOIS W. SOUTHGATE. 

